a x1 x1 a b b a x1 a c c b x1 c x1 a b x1 2.2 a b b a x1 c c b x1 a b b a x1 c b x1 a b b a x1 a c c b x1 c x1 a b x1 true c x1 a b x1 a b b a x1 a c c b x1 a b b a x1 c b x1 a b b a x1 c c b x1 true Failed! NaTT certifiable-1.6